Fluid pump and control therefor



FLUID PUMP' AND CONTROL THEREFOR Filed Jan. 2o, 1944 Patented Jan. 6, 1948 FLUID PUMP AND CONTROL THEREFOR Robert Lapsley, Berrien Springs, Mich., assignor to Clark Equipment Company, Buchanan, Mich., a corporation of Michigan Application January 20, 1944, Serial No. 519,049

s claims. (C1. s- 41) This invention relates to a iiuid pump, and more particularly isconcerned with a iiuid pump of the geared rotor type for developing fluid pressure with means for controlling the operation of the pump in accordance with minimum speed requirements.

In vehicles of the automobile type embodying automatic transmissions, the operation of the control mechanism which in turn actuates the various elements of the transmission is normally controlled by uid under pressure, which fluid actuates suitable pistons for operating the control means.

The present invention is concerned with a pump of the type which is driven from the output shaft of the transmissi-on for developing a fluid pressure which in turn is directed through suitable control means for actuating the various instrumentalities of the automatic transmission mechanism. However, it has been found that under certain conditions such as cold weather when the oil in the uid system may be heavy and viscous the operation of the pump immediately upon starting the vehicle may result in developing a fluid pressure entirely out of line with the desired control due to the thickness of the oil. Therefore, the present invention is directed to a control for a iiuid pump of this type to prevent it from operating below a certain predetermined minimum speed of operation of the vehicle, which speed is preferably a minimum speed below which it is not desired to have the control mechanism operated by the iiuid pressure of the pump become actuated.

One of the primary objects of the present invention is to provide by-passing means within the pump whereby under certain speed conditions the discharge from theoutlet port of the pump will be by-passed back to the suction port without building up any pressure in the discharge side of the pump that might affect the control mechanism. To accomplish this purpose I provide a pump having a passageway interconnecting the discharge and inlet ports which passageway is controlled by a valve mechanism carried by the pump shaft and actuated in response to speed responsive mechanism for holding this passageway open until such time as the vehicle has assumed a predetermined minimum speed.

With such a construction it is apparent that the pump will merely recirculate the uid under pressure without building up any pressure in the pressure side of the control system until the vehicle ls operating above a predetermined min- 2 l control system be rendered operative by the provision of uid pressure. I

Another feature of the present invention is to provide such a construction which can be employed in pumps now available and which is of simple design and of relatively few parts so as to be simple in operation and not requiring v any complicated interlocking control means.

Other objects and advantages of the present invention will appear more fully from the following detail description which, taken in conjunction with the accompanying drawing, will disclose to those skilled in the art the particular construction and operation of a preferred form of the present invention.

In the drawings:

Figure 1 is a sectional view taken substantially on line I-I of Figure 2; and

Figure 2 is an end elevational view of the structure shown in Figure 1.

Referring in detail to the drawing, the shaft 5 is illustrated as being any output shaft of a cated generally by the reference numeral 8 which imum speed at which time it is desired that the provides for distributing fluid under pressure to various clutch means in the gear portion of the transmission and which is described in detail in my copending application Serial No. 526,829 filed 'March 15, 1944.

The bearing 6 as well as the distributing mechanism 1 is supported by means of the partition wall 9 of the transmission which in turn also provides a support for the body member I II of 4a gear pump indicated generally at II The pump II comprises an inner rotor I2 formed with external teeth meshing with the external teeth of an outer rotor I3 mounted eccentrically relative the rotor I2 and driven thereby. Preferably,

the rotor I2 has one le'ss tooth than the rotor I3 thereby providing for differential drive between the two members to produce the desired pumping pressure. The rotor I3 is held in position by means of the cap or end plate member I4 of the pump which is provided with an outlet port or passageway I5 and on the opposite side 0f the structure with a corresponding inlet port I6 which port communicates through the passageway I1 formed in the cap I4 with the arcuate inlet opening I8 shown in Figure 2 opening into a point on the periphery of the inner rotor I2. Similarly, the passageway I5 communicates through the chamber I9 in the plate member I4 with a discharge port 20 leading from the rotors I2 and I3.

The rotor I2 is mounted to be driven by a hollow shaft 22 which shaft extends through the housing II] and is journalled at its outer end in the end plate I4. The shaft adjacent its outer end is provided with laterally directed ports 23 which provide communication from the chamber I9 through the interior of the shaft and outwardly through the end opening 24 of the chamber Il thereby providing a by-pass passageway as indicated by the arrows in Figure 1 for causing fluid from the discharge port 20 to pass through the ports 23 and thence out the end 24 of the shaft into the chamber II thence back to the inlet port I8.

The shaft 22 at its opposite end is provided with a. gear 25 suitably secured to the shaft as by means of the lock nut 26. The gear 25 is in meshing engagement with the gear 1 driven by the shaft so that rotation of the shaft 5 causes lrotation of shaft 22 and, consequently, drives the The plunger 32 is mounted for axial movement n Ln the shaft 22, and is normally urged by the spring 33 into a position so that the headed end 34 thereof is disposed out of register with ports 23 so that under normal conditions when the shaft 22 is operating below a predetermined speed the passageways 23 and 24 will be open to provide for by-passing fluid discharge of port 20 of the pump back to the inlet port I8.

As the speed of the vehicle, determined by the speed of rotation of shaft 5, increases. the gear 25 is correspondingly driven at an increased rate. Depending upon the pressure of spring 33 and the weight of the speed responsive pawls 28, the pawls begin to move outwardly causing the inner ends 29 to exert an axial thrust on the plunger 32 tending to move the end 34'thereof into register with the ports 23. As this speed increases above a predetermined minimum the plunger 32 is forced into a position closing the ports 23 thereby closing the passageway between the dis-f r charge and inlet ports of the pump so that any fluid pressure developed by the pump operating at a speed above this particular minimum speed will be directed outwardly through the chamber I9 and passageway I5 to whatever suitable control devices are to be actuated by the pump.

It is therefore apparent that with this construction, regardless of the viscosity of the oil being pumped by the fluid pump, there will be no pressure built up in the outlet passageway I5 so long as the shaft ,of the pump is operating below a predetermined minimum speed. This means that in cold weather the pump will not.

develop operating pressure in the control system until the speed of the vehicle has increased to a point where operation of the control device of the automatic transmission is desired. When this speed has been reached, the plunger 32 is shifted to close off the valved passageway between the two ports whereupon the fluid pressure developed by the pump is then directed to the con.- trol devices.

I am aware that details of the present construction may be Varied within wide limits without departing from the underlying principles thereof, and I therefore do not intend to be limited except as defined by ,the scope and spirit of the appended claims.

I claim:

1. A fluid pump consisting of rotating gear members, a suction' port and a discharge port for said pump, both located on the same side of said gear members, a shaft for driving said gear members, said shaft projecting beyond said gear members and having a passageway therethrough on the port side thereof providing communication between said ports, a plunger mounted for axial movement in said shaft and normally held in position to maintain said passageway open, and speed responsive means on said shaft for shifting said plunger axially to close said passageway when said shaft is driven above a predetermined minimum speed.

2. A fluid pump comprising a housing, a hollow shaft extending into said housing, a gear rotor in said housing driven by said shaft, an eccentrically mounted internal rotor surrounding and driven by said gear rotor, an outlet port for said pump, an inlet port for said pump disposed on the opposite side of said shaft from said outlet port, said ports both opening into the same radial faces of said rotors, a passageway between said ports disposed beyond said radial faces and having a portion extending through said shaft, and speed-controlled valve means axially slidable in said shaft for closing said passageway when said shaft reaches a predetermined minimum speed.

3. In a transmission having an output shaft, a hollow shaft, means for driving said hollow shaft from said output shaft, a gear pump of the rotor type driven from one end of said hollow shaft and having a suction port and a discharge port, a transverse passageway in the end of said hollow shaft between said ports, a plunger axially shiftable in said hollow shaft and normally urged into position to open said passageway, and speed responsive means on ysaid hollow shaft for shifting said plunger into closing position across said passageway.

ROBERT LAPSLEY.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Armor Aug. 4, 1936 

